AKA: "Wide Youtube", AKA: "Wide video container" - Uses the page space on youtube more efficiently (especially good for high resolutions)
In Firefox? What version? On what page? home/subscriptions/trending etc. Is it always like that or are there special conditions when it happens? Try disabling all other addons and scripts to make sure nothing else is causing the problem.
It's working fine on my end no matter how I resize the window.
You could also check the console if there are errors (F12 then go to console tab). A screenshot might help as well. Thanks. :)
Moves page items off screen
Now I can't click them, in fairness though my monitor isn't THAT big so that may be the problem.